1. Field of the Invention
The present invention relates to a dust cover to be mounted to a suspension mechanism and a dust cover assembly provided with an upper insulator.
2. Description of the Related Art
Conventionally, there has been known a dust cover that is externally fitted onto a shock absorber to cover the area around the protrusion of a piston rod and a dust cover assembly provided with an upper insulator that supports the top end of a coil spring. As the dust cover assembly, as disclosed in Japanese Unexamined Patent Publication No. JP-A-2003-072338 for example, there is a type with the dust cover and upper insulator integrally formed by a rubber elastic body.
By the way, the upper part of the dust cover is integrally connected to the upper insulator, and by having it supported by a piston rod, intrusion of foreign matters from above is prevented. Meanwhile, the lower part of the dust cover is loosely inserted into a cylinder with relative displacement freely allowed therein so that the effect of tensile force against the dust cover at the time of expansion of the shock absorber is avoided.
However, if the gap set between the bottom end of the dust cover and the cylinder is too large, there is a risk of intrusion of foreign matters such as water into the bottom opening of the dust cover to adhere to the piston rod. In addition, there is another risk that a bellows tube portion gets stuck in a state of contraction deformation so that the dust cover is unable to follow the expansion and contraction of the shock absorber.
Then, U.S. Pat. No. 5,954,168 proposes a structure where the bottom part of the dust cover is supported by a cylinder by means of, for example, locking it with a catch lock protruding from the cylinder. In such a structure, the dust cover follows the expansion and contraction of the shock absorber to be forced to undergo contraction deformation, which can exert a tensile force on the dust cover in the axial direction, so that it been studied to improve the durability of the dust cover by making it of resin.
However, if the dust cover is made of resin, it can no longer be formed integrally with the upper insulator that is formed with rubber elastic body for obtaining a buffer effect. In addition, it is difficult to get enough bonding strength by retrofitting the dust cover made of resin to the rubber-made upper insulator. Another idea is to provide the upper insulator with a metal fitting to support the top part of the dust cover, which had a risk of posing a problem with the increase in the weight and the number of parts.